Tool for rolling internal threads



R. c. ZELLER ETAI- 3,491,567

Jan. 27, 1970 TOOL FOR ROLLING INTERNAL THREADS Filed July 5, 1967 2 Sheets-Sheet 1 r INVENTORS: .HUBERT. E.

ZBLLEH, v IELE.

WZHHEN W. WE

Jan. 27, 1970 3 R. C. ZELLER E AL 3,491,567 TOOL FOR ROLLING INTERNAL THREADS 2 Sheets-Sheet 2 Filed July 5, 1967 INVENTORS 1201517512" E. ZELLER.

mum W. WBJEL B.

4y Qu .waws.

United States Patent Office Patented Jan. 27, 1970 TOOL FOR ROLLING INTERNAL THREADS Robert C. Zeller, Fort Wayne Road, and Warren W.

Weihle, 635 Holgate Ave., both of Defiance,

Ohio 43512 Filed July 3, 1967, Ser. No. 650,957 Int. Cl. B21d 3/08 US. Cl. 72-118 11 Claims ABSTRACT OF THE DISCLOSURE An internalthread rolling tool includes a plurality of independently rotatable thread rolls having a single central support and a simplified bearing arrangement for the rolls. The tool is capable of rolling threads in holes of relatively small diameters and can be designed for rolling threads in either blind holes or through holes. In particular, the tool produces threads which are stronger and smoother than those achieved with conventional tools and, further, the tool has an exceptionally long life.

This invention relates to internal thread rolling tools and particularly to such tools capable of rolling threads in relatively small holes.

The internal rolling of threads has a particular advantage over the usual cutting of threads in that the threads themselves are accurate, stronger, and smoother. The threads enable a threaded assembly to withstand greater forces and enable the parts to be assembled or separated more smoothly. A tool for internally rolling threads also has a much longer life than that of a conventional thread cutting tool and, for example, can form from 50,000 to 100,000 pieces compared to 1500 pieces fora conventional internal thread tap.

Internal thread rolling tools have been heretofore proposed but have not been capable of forming threads in relatively small holes and have had limited practicality for rolling threads in any hole because of ditficulties in the manufacture, inaccuracy in the threads rolled, etc.

The present tool is of a unique design incorporating a central support for rotatably supporting all of the thread rolls. The new tool also includes a simplified bearing arrangement for enabling the individual rolls to be independently rotated. The design achieves a tool of long life, one capable of accurately forming threads, and one capable of being employed in relatively small diameter holes.

It is, therefore, a principal object of the invention to provide an internal thread rolling tool having an improved support for the thread rolls an improved bearing design.

Many other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a side view in elevation of a tool embodying the invention and a tool holder, with a workpiece engaged by the tool shown broken away and in section;

FIG. 2 is an enlarged view in longitudinal cross section taken along the line 22 of FIG. 1;

FIG. 3 is a fragmentary side view in elevation, on the same scale as FIG. 2, with parts broken away and in section;

FIG. 4 is a view in transverse cross section taken along the line 44 of FIG. 1;

FIG. 5 is a side view of a central support for the thread rolls;

FIG. 6 is a side view of the thread rolls laid out in a common plane and showing the relative positions and shapes of the thread forming ridges;

FIG. 7 is a fragmentary view in longitudinal section of a modified internal thread rolling tool embodying the invention;

FIG. 8 is a transverse sectional view taken along the line 88 of FIG. 7; and

FIG. 9 is a side view in elevation of a central support for the thread rolls of the tool of FIG. 7.

Referring to FIG. 1, a tool embodying the invention is indicated at 12 and is mounted in a tool holder 14 in alignment with a cylindrical hole or bore 16 of a workpiece 18 supported in a suitable holder 20. One of the holders 14 and 20 is rotated relative to the other or both can be rotated, if desired. The tool 12 includes four thread rolls 22, 24, 26, and 28, a central supporting roll 30, and a holder or housing 32.

The roll holder 32 comprises two main parts 34 and 36. The first part 34 includes a rear shank 38 held by the tool holder 14, a fastening flange 40, and a hub 42. The fastening flange 40 has, in this instance, three fasteners or bolts 44 and a pin 46 between two of the bolts 44 for connecting and aligning the two parts 34 and 36 of the holder 32. The hub 42 has four cylindrical recesses 48 for receiving end portions of the rolls 22-28 and has four annular, conical recesses or surfaces 50 forming portions of outer races for bearings which support the rolls for independent rotation.

The second holder part 36 includes a fastening flange 52, a hub recess 54, a hub 56, and a hub extension 58. The flange 52 has openings 60 and 62 to receive the bolts and pin. The hub and the hub extension have four bearing passages 64 to receive the thread rolls 22-28 and a central bearing passage 66 to receive the supporting roll 30. Annular, conical recesses or surfaces 68 meet the recesses 50 to complete outer races for bearings which rotatably support the thread rolls.

Each of the thread rolls 22-28 includes a thread section 70 comprising a plurality of annular ridges of different, predetermined heights designed to progressively roll the threads in the workpiece. The thread rolls are positioned by means of the passages 64 at angles relative to the longitudinal extent of the tool so that the annular ridges are parallel to the portions of the grooves being rolled in the bore 16. The angle, of course, will depend upon the lead angle or pitch of the threads, a typical angle A being designated as such in FIG. 3. The axis of each of the rolls lies in a plane which is tangential to a circle through the axes of the four thread rolls, which circle lies in a plane perpendicular to the axis of rotation of the tool 12. The angle A is measured between the roll axis and an intersecting line in the tangential plane which is parallel to the axis of tool rotation. For example, with a "32 thread, the angle A is 1 degree, 2 minutes, 40 seconds The thread rolls also include main shanks 72 having rear grooves 74 forming inner races for the bearings, With rear extensions 76 beyond the grooves extending into the recesses 48. Bearing balls 78 are held in the inner and outer races formed by the grooves 74 and the surfaces 50 and 68 to complete the ball bearing supports for the thread rolls. The thread rolls further include forward extensions 80 in front of the thread sections 70 with annular guide grooves 82 therein which meet with the sup porting roll to maintain the four thread sections 70 in proper relationship with respect to one another, the

' ridges of the adjacent thread sections being offset by onequarter pitch, when four thread rolls are used.

The supporting roll 30 has a rear shank 84 received in the passage 66 for rotation therein. The supporting roll further includes an enlarged rear supporting section 86 which engages the main shanks 72 of the thread rolls behind the thread sections 70. An enlarged forward supporting section 88 engages the roll extensions 80 to support the thread rolls in front of the thread sections 70 with the supporting sections 86 and 88 connected by a connecting section 90 of smaller diameter which does not contact or interfere with the thread sections 70. In front of the forward supporting section 88 is a V-shaped guide ridge 91 which cooperates with the four guide grooves 82, also of V-shaped section, to maintain the four thread rolls in precise relative relationship.

A slightly modified tool 92, as shown in FIGS. 7 and 9, is particularly adapted for rolling threads in blind holes and where the threads are intended to extend to a point near the bottom of the hole. The tool 92 includes four thread rolls 94, 96, 98, and 100, and a supporting roll 102 which are independently rotatably held by a holder or housing 104. In this instance, the holder 104 is of threepart construction including a first or rear part 106, a second or intermediate part 108, and a third or forward part 110. The rear part 106 includes a shank 112 and a fastening flange 114 with an annular, conical recess or surface 116 and a concentric recess 118 formed in a hub portion of the rear part 106.

The intermediate part 108 includes a fastening flange 120 and a hub portion 122. The rear face of the hub portion 122 includes a conical, annular recess or surface 124 cooperating with the surface 116 to form an outer race for the bearing with a central passage 126 extending forwardly from the surface 124 through the front face of the hub 122. Four annular, conical recesses or surfaces 128 are formed in the front face of the hub 122 partially to form outer races for bearings of the thread rolls 94- 100, with recesses 129 being behind the surfaces 128.

The forward part 104 includes an outer fastening flange 130, a central recess 132, which receives the hub 122, a forward hub 134, and a hub extension 136. The hub 134 has a central passage 138 extending axially therethrough and in alignment with the passage 126. The rear face of the hub 134 includes four annular, conical recesses or surfaces 140 cooperating with the surfaces 128 to form outer races for bearings, with passages 142 extending for wardly through the hub 134 and the hub extension 136 to receive the thread rolls. The three parts 106, 108, and 110 are held together in proper alignment by bolts 144 and pins 146. The three-part housing enables the roller bear ings for the supporting roll and the thread rolls to be located on different planes, when a roller bearing is desired for the supporting roll.

Each of the thread rolls 94, 96, 98, and 100 includes a thread section 148 which comprises a plurality of annular ridges of predetermined height and shape similar to the thread sections 70 except that fewer of the ridges are employed in the sections 148. The rolls again are located at angles so that the ridges are parallel to the threads at the point of contact therewith, and the threads of adjacent rolls are offset one-quarter pitch. The thread rolls further include main shanks 150, grooves 152 forming inner races for ball bearings, and rear extensions 154 extending into the recesses 129 in the hub 122. Bearing balls 156 complete the ball bearings for the four thread rolls.

The supporting roll 122, in this instance, includes a long main shank 158 with a groove 160 forming an inner race for a ball bearing and a rear extension 162. Ball bearings 164 complete the ball bearing support for the supporting roll. At the front portion of the housing 92, but within the hub extension 136, is an enlarged support 166 which contacts and supports the main shanks 150 immediately behind the thread sections 148.

The tool 92, in this instance, has no projections or extensions of any type forwardly of the thread sections 148 so that the tool can be used to form threads in blind holes with the threads extending to the bottom of the holes. The extension of the supporting roll section 166 to the thread sections, along with the relatively short length of the thread sections, enables this to be achieved. The ball bearings of the rolls 94-100 maintain the thread sections 148 in proper relative positions.

Various modifications of the above described embodiments of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

We claim:

1. An internal thread rolling tool comprising a holder, a plurality of thread rolls extending from said holder and independently rotatably supported thereby, said thread rolls having thread sections for forming internal threads in a workpiece, and a supporting roll located centrally with respect to said holder and extending axially of said holder, said supporting roll having a supporting section contacting said thread rolls adjacent said thread sections.

2. An internal thread rolling tool according to claim 1 wherein each of said thread sections comprises a plurality of annular ridges, said thread rolls being positioned angularly relative to the longitudinal extent of the tool to position the ridges to form grooves in the workpiece when contacting and rotating relative to the workpiece.

3. A tool according to claim 1 characterized further by said supporting roll having an additional supporting section for contacting said thread rolls on the side of said thread sections opposite the first supporting section.

4. A tool according to claim 1 characterized further by said thread rolls and said supporting roll having cooperating means for maintaining said thread rolls in predetermined positions longitudinally of the tool with respect to one another.

5. A tool according to claim 4 characterized by each of said thread rolls having an annular groove at predetermined location thereon and said supporting roll has a ridge at a predetermined location and cooperating with the grooves of all of said thread rolls to hold said thread rolls in predetermined positions.

6. A tool according to claim 1 wherein said thread rolls are mounted in said holder by ball bearings.

7. A tool according to claim 6 wherein said supporting roll is rotatably held in said holder by a ball bearing.

8. A tool according to claim 6 wherein said holder is made in at least two parts and has cooperating annular recesses forming outer races for the bearings.

9. A tool according to claim 8 wherein said thread rolls have annular grooves forming inner races for the bearings.

10. A tool according to claim 7 wherein said holder is made of at least two parts having cooperating annular surfaces forming an outer race for the ball bearing for said supporting roll and said supporting roll has an annular groove forming an inner race for its ball bearing.

11. An internal thread rolling tool capable of rolling threads near the ends of blind holes comprising a holder, a plurality of thread rolls extending from said holder and terminating in thread sections at ends thereof, a central supporting roll rotatably held by said holder and extending centrally of said thread rolls, said supporting roll having a supporting section contacting said thread rolls adjacent said thread sections, between said thread sections and said holder.

References Cited FOREIGN PATENTS 382,699 12/ 1964 Switzerland.

CHARLES W. LANHAM, Primary Examiner LOWELL A. LARSON, Assistant Examiner U.S. Cl. X.R. 72-126 

